If it didn't open up, wouldn't the front of the blades that are supposed to catch and push back (the unsharpened parts) the blades create a "pathway" for the back of the sharpened blades to flow through the tissue, bone, vitals? It might be just my way of thinking but i think anything that the back unopened blades would potentially cut would be pushed out of the way by the front dull parts, and not allow good clean cuts to cause hemmorage.